ww1 was the first global conflict that began with growing tensions across rivaling empires. The well known spark of the war was when the archduke of Austria was assassinated by suburbans. The Allies and Central powers formed after one another declared war on each-other due to treaty obligations. The conflict was a rapidly changing and evolving struggle and led to many massacres and atrocities, particularly in the neutral state of Belgium. Later the Americans entered the war which turned the tides in the allies favor due to the much needed man power and the 4 year long conflict ended in an allied victory. The Treaty of Versailles was harsh on Germany for their involvement in the war and many crumbling empires finally fell, like the ottoman empire.
Oh my, ok thats not really a short summary but yeah